Review of biological indicators for metal mining effluents : a proposed protocol using earthworms

• Main Authors: Sandoval, Maria Claudia, Veiga, Marcello M. (Marcello Mariz), Hinton, Jennifer J., Klein, Bernard
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/10655

There is growing concern about the need for unified criteria on bioindicators used to evaluate the impacts of mine effluents or accidental spills. Toxicological tests based on lethal concentrations (e.g. LC50) have been extensively used to assess effluents, although the biological impact of mining activities cannot always be attributed to acute lethality alone. Geochemical methods, such as sequential or selective chemical extraction, have also been widely used to provide indirect evidence of the availability of metals to organisms. However, the relationship between geochemical parameters, metal uptake, and biological effects is frequently not clear due to complicating interactions between variables. In order to comprehensively characterize risks from mining related discharges, concerns with existing, commonly employed methodologies must be resolved and protocols to assess the effects of sub-lethal or chronic exposure must be established. This paper reviews current understanding of bioaccumulation and bioavailability of heavy metals associated with mining effluents and it explores the concept of the bioaccumulation factor (BAF) and its applicability to mining impacted sites. Existing protocols for assessment of mining related discharges are also compared and a simple, low-cost methodology using earthworms for the evaluation of metal bioavailability in tailings and effluents is proposed. Earthworms are particularly suitable for the assessment of contaminant bioavailability as they are proven metal accumulators and are in full contact with the substrate they consume. As well, they are well studied, easily bred and participate in many food chains and, unlike fish, can be used to assess a variety of media.